1. Technical Field
The present invention relates to a method for mounting integrated circuits on a printed circuit board and, more particularly to a method for mounting tape carrier package type integrated circuits on a printed circuit board.
2. Related Art
Computer systems are information handling systems that are utilized by many individuals and businesses today. A conventional computer system can be defined as a microcomputer that includes a central processing unit (CPU), a volatile memory, a non-volatile memory, a display monitor, a keyboard, a mouse, a floppy diskette drive, a compact disc-read only memory (CD-ROM) drive, a modem, a hard disk storage device, and a printer. Typically, a computer system's main board, which is a printed circuit board known as a motherboard, is used to electrically connect these components together.
The central processing unit is often described as a microprocessor. The microprocessor is an electronic component having internal logic circuitry handling most, if not all, the data processing in the computer system. The internal logic circuitry of microprocessors is typically divided into three functional parts known as the input/output (I/O) unit, the control unit, and the arithmetic-logic unit (ALU). These three functional parts interact together and determine the power and performance of the microprocessor. The combination of the control unit and the arithmetic-logic unit is sometimes referred to as the central processing unit. Also, the combination of the input/output unit, the control unit, and the arithmetic-logic unit is sometimes referred to as the central processing unit.
Microprocessors today are housed in packages that are thin, compact squares. Five common packaging types include the pin grid array (PGA), the multicavity module (MCM) pin grid array, the leadless chip carrier (LCC), the plastic quad flat package (PQFP), and the tape carrier package (TCP). The microprocessor must be mounted to the computer system's main board using a particular mounting procedure.
In general, the tape carrier package type of packaging for a microprocessor begins with a substrate of polyimide film laminated to copper foil. The copper foil is etched in order to form two contact patterns, a first contact pattern that will engage with tabs on the silicon chip of the microprocessor and a second contact pattern that will engage with the computer system's main board.
Consider a tape carrier package (TCP) type Pentium(R) microprocessor as an example of an integrated circuit (IC). The tape carrier package type Pentium(R) microprocessor is an extremely small component including 320 leads as input and output terminals. An interval between the leads is 0.25 millimeters. In addition, such a tape carrier package integrated circuit is relatively small because it does not include any wire-bonded portion that is usually included in other types of integrated circuit packaging. Accordingly, it is possible to fabricate smaller printed circuit boards (PCBS) using the tape carrier package type integrated circuits.
A conventional method for soldering and mounting the tape carrier package type integrated circuit on the printed circuit board (PCB) shall be described hereinafter. First, contaminating particles attached on the printed circuit board transferred from a previous process are removed by an air gun. A conductive bond is applied to predetermined portions of the aforementioned second contact pattern on the printed circuit board.
Thereafter, a flux is applied to the same portions of the second contact pattern on the printed circuit board that have been already applied with the conductive bond. The tape carrier package type integrated circuit that has been processed in a cutting and forming process is aligned with the second contact pattern applied with the flux. In other words, the aforementioned first contact pattern engaging with tabs on the silicon chip of the microprocessor is aligned with the second contact pattern applied with the flux.
A holding block is moved onto and covers the integrated circuit aligned on the printed circuit board. A light beam is applied to the integrated circuit to solder the integrated circuit on the printed circuit board. After the integrated circuit is soldered on the printed circuit board, the printed circuit board and the holding block are cooled.
However, since the steps of applying the flux, aligning the integrated circuit, and soldering the integrated circuit are carried out successively in one tool, a great amount of time is required for fabricating the printed circuit board. To overcome such a disadvantage, a method for mounting the integrated circuit on the printed circuit board in a shorter time has been provided. In the method, applying the flux to the printed circuit board and aligning the integrated circuit on the printed circuit board are carried out in a mounting apparatus, and soldering the integrated circuit on the printed circuit board is carried out in a soldering apparatus, separately.
However, the above method also suffers a disadvantage that the integrated circuit aligned on the printed circuit board may be disordered while the printed circuit board with the integrated circuit aligned thereon is transferred to the soldering apparatus.
Exemplars of recent efforts in the art include U.S. Pat. No. 5,704,116 for a Method of Holding a Component Using an Anhydride Fluxing Agent issued to Gamota et al., U.S. Pat. No. 5,425,495 for a Hot Air Circulation Method for Wave Soldering Machines issued to Gibson, U.S. Pat. No. 5,175,410 for an Ic Package Hold-down Fixture issued to Freedman et al., U.S. Pat. No. 5,646,441 for a Tcp Tab Design with Radial OuterLeads issued to Hasan et al., and U.S. Pat. No. 5,729,051 for a Tape Automated Bonding Type Semiconductor Device issued to Nakamura.
Although various integrated circuit mounting procedures currently exist, I have discovered that there is a need to provide an enhanced mounting procedure which can be utilized in order to mount an integrated circuit to a printed circuit board in an improved manner.